In general, the art involving valves for handling pressurized gases is highly developed and a large number of designs have been known for many years and have long been in successful operation. Many competing designs are available in the marketplace and such designs have been successfully modified for application to a wide variety of specific uses. This art has, however, developed primarily in connection with relatively large valves, such as valves adapted for connection to conduits of at least about 1/4 inch internal diameter (1/8 NPT pipe) and arranged for supplying, for example, air cylinders of one inch in diameter and having one stroke of up to 8 inches.
However, in addition to the foregoing, there has over the past several years been developing a series of applications for electrically operated valves for controlling a pressurized gas, which valves are extremely small and are adapted for supplying a very small load, such as an air cylinder of 3/8-1/2 inch in diameter and having a stroke of up to 3 inches. Inasmuch as the cylinder to be so supplied is very small, the valve by which it is to be supplied should be correspondingly small. Nevertheless, for reasons of uniformity in design, convenient commercial availability of pipe, resistance to physical damage, and to minimize pressure drop from one end of a conduit to another, the line through which such valve and cylinder is supplied should be as large as possible and in any case seldom less than 1/8 NPT pipe (0.265 inch internal diameter and 0.406 inch external diameter).
While many valves have been offered to the market over the past several years for meeting these conditions, and some of them have been accepted and used, the valves previously available have at best been only partially satisfactory. Specifically, they have in general been reasonably successful in operation but they have been based on the designs of larger valves and when made in small sizes have often produced extremely awkward and consequently expensive manufacture and assembly problems and further they have often not been well adapted to accepting conduit in the minimum size above indicated. This can be readily understood when it is appreciated that the valves through which this art has primarily developed, such as a valve which has been offered to the industry for a substantial period of time under U.S. Pat. Nos. 3,251,378 or 2,912,009, wherein said valves are of the order of 43/8 inches long by 15/8 inches in diameter including the valve portion, create serious design problems when same are reduced to a size approximately 11/8 inches in diameter or 11/8 inches square, and 2 7/16 inches in length.
One particularly difficult problem in the provision of valves of small sizes, related to but separate from the foregoing, is the problem of manufacturing tolerances in that tolerances which can be accepted and which present no great difficulty in the manufacture, assembly or operation of a relatively large valve have a serious and often adverse effect on the assembly and operation of a very small valve. On the other hand, to reduce the manufacturing tolerances materially will excessively increase the cost of the manufacturing operation. It is therefore necessary to arrange a small valve in such a manner that normal manufacturing tolerances can be accepted, and the variations resulting therefrom absorbed, without creating assembly or operating problems.
A further problem involved in the design of such small valves as aforesaid, especially small four-way valves, arises out of the fact that it is for some uses desirable to provide in valves of physically small size the operating characteristics of the larger valve. For example, in providing control panels for the manufacture of small articles such as semi-conductors or watches, the processing machine though complex is relatively small and hence it is undesirable to have the large control system which would be required by the use of large valves. Thus, a substantial need exists and has existed for a long time for very small four-way valves with a capacity and capability for use with pipe sizes characteristic of large valves but which are themselves of much smaller size than previously considered necessary.
Still a further problem with such small valves, especially four-way valves, stems from the desire to use such valves in combination with an electrical operator, specifically a solenoid. The known four-way valves, even those believed to be of small size, have necessarily utilized a valve stroke of substantial length. Since the valve stroke must be provided by the solenoid, and inasmuch as the power requirements of the solenoid, and hence the size, increases in proportion to the square of the stroke, this necessarily requires a solenoid of substantial size so that same is unacceptable for use in situations requiring a miniature valve and operator.
Another problem encountered has been the increased turbulence of the air flowing through the valve from the inlet port to the load ports. This increased turbulence has prevented the successful design of a truly miniature four-way valve in that it has prevented the valve from operating in the desired manner.
Accordingly, the objects of the invention include:
1. To provide a four-way valve for controlling the flow of a pressurized gas, which valve will be efficient and reliable and can be economically produced in very small sizes.
2. To provide a four-way valve, as aforesaid, which when produced in the very small sizes indicated will still be sturdy and reliable over a long period of time of high-speed repetitive operation.
3. To provide a four-way valve, as aforesaid, of construction which, even though made in the very small sizes aforesaid, will still permit the use of conventional tolerances so as to be economical to manufacture, while still being efficient in operation.
4. To provide a four-way valve, as aforesaid, which in spite of its very small size can be efficiently associated with conduits of sizes normally used for larger valves.
5. To provide a four-way valve, as aforesaid, which in spite of its very small size will have the performance characteristics, including capacity, of previously known larger valves.
6. To provide a valve, as aforesaid, which has an extremely small valve stroke so that it can be actuated by an electrical operator, particularly a solenoid, of extremely small size and power.
7. To provide a valve, as aforesaid, which utilizes a liner positioned in surrounding relationship to a slidable valve plunger and constructed from two identical sleevelike members disposed in end-to-end relationship, said two members cooperating to define an intermediate flow control chamber having opposed tapered surfaces which function as valve seats and coact with a resilient seal ring on the plunger for controlling flow from the inlet port.
8. To provide a valve, as aforesaid, wherein the opposed tapered valve seats extend at a steep angle relative to the direction of movement of the valve plunger and confine the resilient seal ring therebetween for limiting the stroke of the plunger while permitting the stroke to be extremely small.
9. To provide a valve, as aforesaid, wherein the tapered valve seats are preferably provided with a curved or concave configuration to thereby increase the clearance around the resilient seal ring, which clearance is believed to minimize turbulence as the air flows past the seal ring from the inlet port to the selected load port.
Other objects and purposes of the invention will be apparent upon examination of the accompanying drawings and study of the following specification.